Printing devices include electrophotographic (EP) (i.e., xerographic) printing devices, such as laser printing devices like laser printers. EP and other types of printing devices use halftoning as a way to reproduce continuous-tone images using binary tones. For example, each part of a digital image to be printed may have for a given color a particular tone, or intensity, of this color, ranging from a minimum tone or intensity to a maximum tone or intensity. However, most types of printing devices can actually output colorant such as toner in just a binary manner: for a given color, each part—such as each pixel, each portion of each pixel, or other picture element location—is printed at a maximum tone or intensity or is not printed at all.
Halftoning reproduces continuous-tone images using binary tones. A tone reproduction curve (TRC) corrects the tones of an image prior to halftoning being performed. The TRC may also be referred to as a tone response curve. A TRC is applied to a desired tone value, to adjust for dot gain and other characteristics of a given printing device and/or a given printing device type. More specifically, a TRC is applied to a digital image prior to printing, so that the tone or intensity of each part of the printed image optimally approximates the tone or intensity of the corresponding part of the original digital image. Using a TRC thus ensures that the printed image optimally better reflects the digital image, from the perspective of the human visual system (HVS).